1. Field of the Invention
The present invention relates to a projection television and, more particularly, to an optical system for a projection television.
2. Background of the Related Art
A conventional projection television is a device for magnifying and projecting image light generated from an image display means onto a projection surface such as a screen. As shown in FIG. 1, the conventional projection television comprises a cabinet 10 with a screen 11 exposed to the outside, a reflection mirror 20 installed inside the cabinet 10, an optical system 30 and a light source 40. The light source 40 generates a light to irradiate on the optical system 30 and the optical system 30 generates an image light to arrive on the reflection mirror 20, whereby the image light is projected to form an image on the screen 11.
Generally, an LCD (Liquid Crystal Display) or a DMD (Digital Micromirror Device) is adapted to an image display means for generating an image light for the optical system 30. Since the LCD has disadvantages of manufacturing difficulty and low brightness, the DMD is widely used recently. The DMD is used for a DLP (Digital Light Processing) system, which is an optical switch display element for changing the angle of a micro-mirror between +10 degrees to −10 degrees to switch between two modes of the reflection angles of lights. FIG. 2 is a perspective view schematically showing an optical system having a DMD for a conventional projection television.
As shown in FIG. 2, the optical system 30 comprises a DMD panel assembly 31 with a plurality of micro-mirrors, and a projection lens assembly 32, and is disposed at a base frame 12. A light irradiated from the light source 40 (see FIG. 1) is reflected by the micro-mirrors of the DMD panel assembly 31 onto the projection lens assembly 32, and the reflected image light is projected to a projection surface such as the screen 11 (see FIG. 1) to be displayed.
With the above construction of the optical system for the conventional projection television, the DMD panel assembly 31 is adjusted by hand or an additional control device disposed at the projection lens assembly 32 is used in order to adjust the tilt angle of the image light or a position at which an image is projected.
When the DMD panel assembly 31 is fixed by using clamps such as screws after the tilt angle of the DMD panel assembly 31 is adjusted by moving the DMD panel assembly 31 by hand, the problem occurs in that a precise adjustment of the tilt angle is difficult.
On the other hand, when the additional control device is disposed at the projection lens assembly 32, the problem occurs in that the structure of the projection lens assembly 32 becomes more complex.